Objectives: Many patients with Parkinson's disease (PD) suffer from non-motor symptoms like sleep disturbances, excessive daytime sleepiness and fatigue. The aim of our research was to explore whether fatigue is related to sleepiness and sleep problems, depression and functional status, controlled for age, gender and disease duration.
Methods: The sample consisted of 78 PD patients from Eastern Slovakia (52% males, mean age 68.8+/-8.7, mean disease duration 7.2+/-6.8). The Multidimensional Fatigue Inventory (5 dimensions), the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, Hospital Anxiety and Depression Scale and the Unified Parkinson's Disease Rating Scale were used. Demographic data were obtained in a structured interview. Multiple linear regression was used to analyse the data.
Results: Sleepiness did not show significant association with fatigue in any of the fatigue domains; neither did quality of sleep. Depression was significantly associated with all domains of fatigue, the strongest being the relationship with general fatigue (beta .42), reduced motivation (beta .39), mental fatigue (beta .35) (p<.001), and physical fatigue (beta .31) (p<.01), while the relationship with reduced activity was less strong (beta .22) (p<.05). Worse functional status was significantly related to reduced activity (beta .50), general fatigue (beta .35), physical fatigue (beta .35), and mental fatigue (beta .35) (p<.001).
Conclusion: Fatigue is not related to daytime sleepiness or night-time sleep dysfunction. Fatigue is more strongly influenced by the presence of depression and worse functional status.